Omg courage to you really. I know it's difficult and sometimes we are tempted to bury them alive in the garden because they are so fucking stubborn, but it's the part of the game, so here we are now xD. You have so much patience, because in my case it's more shocking. She is older than me, she should be the one to say to me what I am doing right now, since several months. Lost cause. Lost cause I told you. His biais is too strong, the man litteraly stole her brain, mind, everything. But fortunately she doesn't spend a centime about their merch and others unusful stuff. But she is very obssessed with the contents like Mvs and live. She looks the show only for her biais. She doesn't really care about the others, so in my bad luck, I can even see good lights. In these moments I said to myself that its still better than her acting like a Sasaeng or to be fond about ALL the members. Just one is enough xD
I don't judge your sister of course, we all have spend money in things sometimes ridiculous, but still for BTS? That's too much for what they show. Hope she will start understand that something is weird and trouble with them.
She has chance that you look out for her